How to open a file in mojo?

[amarouane-ABDELHAK]

I am trying to read a file using mojo but didn't find any example in the getting started documentation

[rarebreed]

I don't believe there is a way to do this through any mojo library. but you can do it through python

Welcome to Mojo! 🔥
Expressions are delimited by a blank line.
Type `:mojo help` for further assistance.
1> let bn = Python.import_module("builtins")
2. let f_hand = bn.open("learning.mojo", "r")
3. let body = f_hand.read()
4. print(body)
5. 
from python import Python

fn run(cmd: String) raises -> None:
    let sp = Python.import_module("subprocess")
    let result = sp.run(
        ["ls", "-al"],
        None,     # stdin
        None,     # input
        sp.PIPE,  # stdout,
        sp.PIPE,  # stderr
        True,     # capture_output
    )
    print(result.stdout)

Since I don't believe mojo supports Context Managers yet, you will need to call the close() method on the file object.

[rd4com]

you can use this if you want by syscall read into string or ish/shim

[rarebreed]

Ah nice, I was wondering how to make system calls like an fopen or fstat. Nice to know about the external_call intrinsic

[rd4com]

yes, i got happy when i discovered it too, and it is quite intuitive

[felixf4xu]

as for v0.6.1, you can:

import pathlib

fn main():
    let p: Path = Path("./test.txt")
    try:
        let str : String = p.read_text()
        print(str)
    finally:
        pass   

[gryznar]

Is this try...finally needed? It looks like, it does nothing

[felixf4xu]

Is this try...finally needed? It looks like, it does nothing

you can try to remove them and see the compiler errors 😁

[treeshateorcs]

you can open a file with with open now:

fn main() raises:
    with open("file", "r") as file:
        print(file.read())

[davidxiaozhi]

Thanks everyone very much for your solution, which can temporarily solve my problem of reading small files. For large files, I expect to read and process them line by line by reading until the \n character is encountered, instead of reading the entire file at once.